Cosolvency Effects Research Articles

High Pressure Vapor–Liquid Equilibrium Data for the Quaternary Carbon Dioxide + 1-Decanol + 3,7-Dimethyl-1-octanol + n-Dodecane System

Vapor–liquid equilibrium (VLE) data were measured for the quaternary system containing CO2, n-dodecane (nC12), 1-decanol (C10OH), and 3,7-dimethyl-1-octanol (37DM1O). The data were measured using a previously constructed static-analytic setup at temperatures between 308 and 348 K and pressures up to 19.2 MPa. The measured data indicated signs of a temperature inversion in the 1-decanol-rich mixtures. The relative solubility analysis revealed that the components in the 1-decanol-rich mixtures could be separated with greater ease than the components in the n-dodecane-rich mixture. The greater difficulty associated with separating components in the n-dodecane-rich mixture is likely linked to cosolvency effects which cause pinches in separation. The data were modeled in Aspen Plus, using the RK-ASPEN model. The modeling results highlighted the need for fitted solute–solute interaction parameters. However, even with the inclusion of these parameters there still exists significant deviation between the experimental and predicted data. The RK-ASPEN model can, therefore, only be used to approximate VLE data for the system.

Modeling Gel Swelling in Binary Solvents: A Thermodynamic Approach to Explaining Cosolvency and Cononsolvency Effects

If gel swells in binary solvents, two unusual phenomena may appear. Two solvents with relatively low swelling ability may become a good solvent for the polymer with high swelling ability when mixed, which is known as a cosolvency effect. In contrast, a cononsolvency effect indicates polymer is less soluable in solvent mixtures than it is in each of the cosolvents. In this work, we develop a thermodynamic theory to describe the equilibrium swelling behaviors of gels in binary solvents based on the Flory–Huggins lattice model. The model can reproduce both cosolvency and cononsolvency effects, showing that these effects are caused by the preferential absorption of the solvent by polymer together with solvent–solvent interactions. The model is also applied to describe experimentally observed cosolvency and cononsolvency effects in the literature, which shows an acceptable agreement.

Super- and near-critical fluid phase behavior and phenomena of the ternary system CO2 + 1-decanol + n-tetradecane

High-pressure phase behavior of six 1-decanol+n-tetradecane (solute+solute) mixtures in the presence of near- and supercritical CO2 (solvent) were experimentally studied between T=300K and T=358K using a visual static synthetic method. CO2 free or reduced n-tetradecane mass fractions (wcred) of 0.2405, 0.5000, 0.6399, 0.7698, 0.8162 and 0.9200g.g−1 were selected for the mixtures and the solute (i.e. combined 1-decanol+n-tetradecane) mass fractions (ws) were varied between 0.015g.g−1 and 0.65g.g−1. The ternary system displayed temperature inversions at T=308K and T=318K for the mixture wcred=0.2405g.g−1. For all other wcred mixtures, an increase in temperature leads to an increase in pressure. A liquid-like (bubble-point) isotherm and a vapor-like (dew-point) isotherm were used to graphically define the size and range of isothermal cosolvency effects in the ternary system. The data were used to construct ternary phase diagrams from which cosolvency effects were observed for each set temperature. The large occurrence of cosolvency lead to the penetration of the liquid-liquid-gas (l1l2g) three-phase surface, forming a two-phase liquid-gas (l-g) hole between wcred=0.7698g.g−1 and wcred=0.9200g.g−1. Closed isobaric miscibility windows were inferred for wcred=0.8162g.g−1 to classify the ternary system as Class T-IV phase behavior.

Thermodynamics of Water-Air Transfer of Fuel Oxygenates by the Dynamic Method of Batch Air Stripping: Experimental Study of Temperature and Cosolvency Effects

The thermodynamics of the mass transfer process of fuel oxygenates (MTBE and ETBE) from aqueous phase to air by batch air stripping (BAS) has been studied in this work. This study analyzes the influence of the aeration flow and the temperature. The Mackay approach was used in order to calculate the Henry's law constant for each operational condition and they were compared with those obtained by static methods. The thermodynamics functions of the process, aqueous free excess enthalpy of solution () and enthalpy of air-water transfer (Δwa Hi ) for both compounds were calculated and compared with literature values. Finally the effect of the cosolvency of tert butyl alcohol (TBA) was analyzed.

From polyelectrolyte to polyampholyte microgels: comparison of swelling properties

We report the results of comparative studies of the swelling behavior of polyelectrolyte (PE) and polyampholyte (PA) microgels in response to pH, ionic strength, temperature, and solvent composition. Polyelectrolyte microgels used were cross-linked binary copolymers of poly(N-isopropylacrylamide) (polyNIPAm) and acrylic acid (AA) or vinyl imidazole (VI). The PA microgels with an excess of either cationic or anionic groups swelled at low or high pH values, respectively, analogous to PE microgels. The PA microgels with similar amounts of AA and VI groups exhibited marked swelling at both high and low pH values. All PA microgels shrank in the intermediate range of pH due to electrostatic attraction between charged AA and VI moieties. In moderately concentrated salt solutions, PA microgels underwent swelling showing antipolyelectrolyte behavior. The extent of swelling of PA microgels increased with rise in AA content. The temperature-dependent contraction of both PE and PA microgels occurred at higher temperatures when AA and VI groups were charged and hydrophilic. Ion pairing between the AA and VI groups increased the extent of the temperature-induced deswelling in PA microgels. The solvent-dependent swelling of PE and PA microgels in ethanol–water mixtures was governed by competing electrostatic and cosolvency effects.

New phase phenomena in ternary systems at high pressures – Cosolvency and miscibility windows up to 100 MPaElectronic supplementary information (ESI) available: tables of experimental data. See http://www.rsc.org/suppdata/cp/b1/b109224n/

For selected systems CO2 + alkan-1-ol + alkane, new high-pressure phase phenomena have been found. Isobaric cosolvency effects and isothermal miscibility windows are presented phenomenologically and numerically. Additionally, rules for the occurrence of these effects are given.

Complex phase equilibrium phenomena in fluid ternary mixtures up to 100 MPa: cosolvency, holes, windows, and islands—review and new results

During recent years some special phase equilibrium phenomena, such as cosolvency and related effects, have been considered in greater detail and it could be shown that carefully selected type III carbon dioxide binaries exhibiting gas–gas like fluid phase behavior can be combined to give a ternary system, which might show large cosolvency effects with improved mutual miscibility (in comparison with the binaries) and, as a consequence, two-phase liquid–gas holes in the three-phase liquid–liquid–gas surface and/or one-phase miscibility windows surrounded by heterogeneous states. As examples selected carbon dioxide+1-alkanol+alkane systems were intensively investigated; for reviews see [1–4]. In the present manuscript a review of these investigations is given and new results on carbon dioxide+alkanoic acid+alkane systems at pressures up to 100 MPa are presented. Here, in particular, phase equilibrium data of the systems carbon dioxide+undecanoic acid+hexadecane and carbon dioxide+decanoic acid+tetradecane is given where cosolvency and windows have been found. In addition, phase equilibrium data is presented for the system carbon dioxide+decanoic acid+1-dodecanol, which shows reduced mutual miscibility (in comparison with the binaries) and corresponds to an island system. Thus, it exhibits a phase behavior that is more or less opposite to that of the systems mentioned above. The results are discussed from a thermodynamical and phase-theoretical point of view.

Complex Phase Equilibrium Phenomena in Fluid Mixtures up to 2 GPa−Cosolvency, Holes, Windows, Closed Loops, High-Pressure Immiscibility, Barotropy, and Related Effects

First, the most important experimental techniques are briefly reviewed, including the diamond anvil cell (DAC) technique. As a first example, it is demonstrated that carefully selected type III carbon dioxide binaries exhibiting gas-gas-like fluid phase behavior can be combined to give a ternary system, which might show large cosolvency effects and, as a consequence, two-phase holes in the three-phase liquid-liquid-gas surface and/or one-phase miscibility windows surrounded by heterogeneous states (e.g., carbon dioxide + 1-decanol + tetradecane). As a second example, type VI binary systems exhibiting closed immiscibility loops in isobaric temperature (composition) diagrams are considered. With increasing pressure, such closed loops can shrink or even disappear completely (e.g., tetrahydrofuran + water); have a tube-like shape, often with a narrowing at medium pressures (e.g., 3-aminopentane + water); or even appear at high pressures only (so-called high-pressure immiscibility, e.g., tetra-n-butylammonium bromide + water). Finally, isopycnic and barotropic effects are discussed in relation to the phenomena described above.

Fluid phase equilibria of (carbon dioxide + a 1-alkanol + an alkane) up to 100 MPa andT = 393 K: cosolvency effect, miscibility windows, and holes in the critical surface

Phase equilibria phenomena such as cosolvency effects, miscibility windows, and non-critical (liquid + gas) (l.g.) holes in the critical surface in (carbon dioxide + a 1-alkanol + an alkane) were studied up to 100 MPa. In continuation of experiments by Kordikowski and Schneider and Pöhler et al., carbon dioxide systems containing a 1-alkanol withm⩽ 10 and an alkane with n⩽ 16 (where m and n denote the number of carbon atoms in the alkyl chains of the 1-alkanol, or the alkane, respectively) were investigated for large cosolvency effects. An isothermal cosolvency effect of 14 MPa has been found in (carbondioxide + 1- octanol + hexadecane) at T= 298 K with additional exhibition of large isobaric miscibility windows. Non-critical l.g. holes in the critical surface are also experimentally established. These l.g. holes in the critical surface, which have already been described as l.g. two-phase holes in the (liquid + liquid + gas) (l.l.g.) three-phase surface by Patton et al. and Peters et al., are now deduced from the occurrence of cosolvency effects when cosolvency lowers the critical surface of a ternary system onto the l.l.g. three-phase surface. This can ultimately lead to a penetration of the l.l.g. three-phase surface by the critical surface with the exhibition of a, mostly closed-loop, critical end point locus as the intersection line, surrounding a non-critical l.g. region. The relation between miscibility windows and holes in the critical surface is illustrated by the examination of systems exhibiting both miscibility windows and holes such as (carbon dioxide + 1-heptanol + pentadecane) and (carbon dioxide + 1-decanol + tetradecane).

Cosolvency effects, miscibility windows and two-phase lg holes in three-phase llg surfaces in ternary systems: a status report

During the present decade, many experimental results on phase equilibria phenomena such as cosolvency, miscibility windows, and two-phase lg holes in three-phase llg surfaces (non-critical lg holes in the critical surface) in ternary systems were obtained by various research groups. It is the aim of this paper to collect and sort these results in order to present a summary and a status report of experimental and theoretical research in this field. The emphasis will be on ternary systems of near- and supercritical carbon dioxide with one polar and one non-polar component (here mostly a 1-alkanol and an alkane). It will be demonstrated how cosolvency effects influence the appearance of miscibility windows as well as the occurrence of two-phase lg holes in the three-phase llg surface and how these phenomena are related to each other.

Cosolvency Effects of Monoethanolamine and Triethanolamine: Implications for the Remediation of Benzene in Groundwater at Sour-Gas Plants

Studies were conducted to measure the cosolvency effect of monoethanolamine (MEA) and triethanolamine (TEA) on the aqueous solubility of benzene in support of the remediation of contaminated subsurface environments at gas plants in western Canada. Experiments utilized sodium chloride solutions of the amines in the concentration range of 0–0.065 volume fractions, and non-saline waters in the range 0–1 volume fractions. The measured values of the cosolvency power σ for MEA and TEA, based on the log-linear model, were 1.86 ± 0.05 and 2.21 ± 0.04, respectively. The corresponding values for the semi-cosolvency power σ0.5 were 1.22 ± 0.005 and 1.19 ± 0.005, respectively. It is postulated that the difference in the values of σ and σ0.5 may be linked to cosolvent polarity of the amines in water. In 0.2 Mol/L NaCl saline water, the solubility of benzene increased linearly from 1660 mg/L to 2170 mg/L and 1960 mg/L for cosolvents MEA and TEA (0–0.065 volume fractions), respectively. As evidenced by the measured 30% increase in the solubility of benzene, remediation strategies of groundwater at sour-gas plants should therefore take into account the levels of these amines and their effects on the transport of hydrocarbon contaminants.

Fluid phase equilibria of binary and ternary mixtures of supercritical carbon dioxide with a 1-alkanol and an n-alkane up to 100 MPa and 393 K—cosolvency effect and miscibility windows (Part II)

Cosolvency effects and miscibility windows were studied in selected ternary systems containing a supercritical solvent (CO 2), a 1-alkanol (1-nonanol to 1-undecanol) and an n-alkane as the third component ( n-pentadecane to n-octadecane) according to the analytical method. In the present experiments the ranges of temperature and pressure were 288 K to 393 K and 7.5 MPa to 100 MPa respectively. A new technique (so-called quasi-synthetic method) is described to determine critical parameters of binary mixtures from synthetic measurements performed with the gaseous component being the pressurizing medium. It is the aim of the present investigations to give a quantitative description of the cosolvency effect as a function of temperature and of the chain lengths of the 1-alkanol and the n-alkane respectively, as a continuation of the systematic investigations of Kordikowski and Schneider (1993) as well as of Pöhler and Schneider (1995). In order to compare systems with or without a pressure minimum on the ternary critical line at a constant temperature, a mean cosolvency effect was introduced, being a measure for improved solubility in ternary systems which expresses itself by a positive curvature of the ternary critical line at constant temperature.

Cosolvency Effects on Sorption of a Semipolar, Ionogenic Compound (Rhodamine WT) with Subsurface Materials

The sorption of rhodamine WT (RWT), a semipolar ionizable fluorescent dye, from methanoljnvater and acetone/water mixtures was investigated using batch and column studies with two natural subsurface media. The utilities of cosolvency, solubility, and sorption theories were evaluated. The effect of cosolvents on sorption of RWT showed significant deviations from the log-linear cosolvency model. The observed cosolvency effects on sorption are qualitatively consistent with that expected for semipolar solutes or for organic acids. However, the quantitative application of either the semipolar cosolvency model or the cosolvency model with speciation could not adequately describe the observed behavior. The magnitude of the cosolvency effect differed for the two subsurface media

Cosolvency effects of benzyl alcohol and heptane on the formation of macroporous styrene-divinylbenzene copolymers

Styrene-divinylbenzene copolymers were synthesized by suspension polymerization in the presence of benzyl alcohol (BA) and hepatane (Hep). The influence of BA/Hep ratio, dilution degree and DVB content on the formation of porous structure and swelling of the copolymers were investigated. The results were interpreted according to the solubility parameter theory.

Fluid phase equilibria of binary and ternary mixtures of supercritical carbon dioxide with low-volatility organic substances up to 100 MPa and 393 K: c

Kordikowski, A. and Schneider, G.M., 1993. Fluid phase equilibria of binary and ternary mixtures of supercritical carbon dioxide with low-volatility organic substances up to 100 MPa and 393 K: Cosolvency effects and miscibility windows. Fluid Phase Equilibria 90: 149-162. Isothermal p( w) diagrams at 353.2 and 393.2 K as well as isobaric T( w) diagrams at 25 MPa were determined for binary mixtures of CO 2 with 1-dodecanol and the n-alkanes hexadecane nonadecane, eicosane and tetracosane. In addition measurements were taken for the ternary systems CO 2 + n-alkane + 1-dodecanol (where n-alkane = hexadecane, nonadecane, eicosane or tetracosane) under the same conditions of temperature and pressure. For the system CO 2 + nonadecane + 1-dodecanol additional experiments were carried out at 308.2 K. The resulting ternary critical curves exhibit ‘cosolvency effects’ and ‘miscibility windows.’

Cosolvency effects on copolymer solutions at high pressure

AbstractCloud‐point data to 180°C and 2800 bar are presented for polyethylene, poly(methyl acrylate), and two poly(ethylene‐co‐methyl acrylate) copolymers (10 and 31 mol % methyl acrylate) in propane and chlorodifluoromethane with two cosolvents, acetone and ethanol. The addition of small amounts of either cosolvent to the copolymer–solvent mixtures shifts the cloud‐point curve to lower pressures and temperatures, as both cosolvents provide favorable polar interactions with the acrylate group in the backbone of the copolymer. Ethanol has a larger effect than acetone since ethanol hydrogen bonds to the acrylate group. However, if the concentration of ethanol is increased above ca. 10 wt %, it self‐associates and reverts to antisolvent behavior, forcing the copolymer out of solution. For nonpolar polyethylene–propane mixtures, the polar cosolvents behave as traditional an‐tisolvents. In poly(methyl acrylate)–chlorodifluoromethane mixtures, both polar cosolvents enlarge the single‐phase region. The cloud‐point curves for the (co)polymer–propane–acetone mixtures are modeled reasonably well using the Sanchez–Lacombe equation of state with two adjustable mixture parameters. No attempt is made to model the mixtures that exhibit hydrogen bonding. © 1993 John Wiley & Sons, Inc.

Phase equilibrium investigations of fluid systems at high pressures

Abstract

Preferential solvation in polymer cosolvent systems: Polystyrene + cyclohexane + ethanol and poly(vinyl‐2‐pyridine) + nitromethane + carbon tetrachloride

AbstractTwo cosolvent systems are studied by light scattering and viscosity measurements. The cosolvency mechanism is discussed in relation to the preferential adsorption, solubility parameter, and excess free energy of mixing of the two liquid components. The cosolvency effects are attributed to a “true” and an “apparent” cosolvency.